User’s manual Updated: March 7, 2011 Printed: January 3, 2012
© Light Conversion Ltd. P/O Box 1485, Saulėtekio al. 10 LT-10223 Vilnius, Lithuania Email:
[email protected] Web: http://www.lightcon.com Support:
[email protected]
1 PREFACE
This manual contains user information for safe installation and operation of PHAROS laser system. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ Read this manual carefully before operating laser for the first time. Special attention must be given to material in chapter “LASER SAFETY” that describes safety hazards and precautions against them. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ Use of controls, adjustments or procedures other than those specified in this manual may result in exposure to hazardous radiation and/or damage of equipment. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
Thank you for using Light Conversion products.
Support needs If you have any technical questions or problems please contact our authorized representative or Light Conversion directly:
Light Conversion Ltd. Keramiku 2b, LT-10233 Vilnius, Lithuania Email:
[email protected] Web: http://www.lightcon.com
2
1.1 Electrical and Environmental Specifications Electric*
110VAC, 50-60Hz, 20A 220VAC, 50-60Hz, 10A
*Chillers used with PHAROS require appropriate commutation of the mains transformer located inside the chiller. * Some models of High Voltage supplies used with PHAROS laser system are designed for single mains voltage (110VAC or 220VAC).
For Indoor use only Altitude Operating temperature Relative humidity
Up to 2000 m 15-30°C (air conditioning recommended) 20-80% (non- condensing)
3
Table of Contents User’s manual ............................................................................................................................. 1 1
PREFACE........................................................................................................................... 2 1.1
2
3
LASER SAFETY ............................................................................................................... 6 2.1
Optical safety. .............................................................................................................. 6
2.2
Electrical safety............................................................................................................ 7
SYSTEM DESCRIPTION AND SPECIFICATIONS ..................................................... 11 3.1
PHAROS configuration ............................................................................................. 11
3.2
Oscillator .................................................................................................................... 14
3.3
Stretcher/compressor ................................................................................................. 14
3.4
Regenerative amplifier ............................................................................................... 14
3.5
Mechanical design ..................................................................................................... 18
3.5.1
Regenerative amplifier ....................................................................................... 20
3.5.2
Oscillator ............................................................................................................ 25
3.5.3
Stretcher/compressor .......................................................................................... 30
3.5.4
Pockels cell driver and High voltage supply ...................................................... 32
3.6 4
Specifications ............................................................................................................. 34
Operation and maintenance of the system ........................................................................ 35 4.1
Installation ................................................................................................................. 35
4.2
Quick start .................................................................................................................. 40
4.3
Switching-off ............................................................................................................. 41
4.4
Setting parameters ...................................................................................................... 42
4.4.1
Setting pump current regenerative amplifier ...................................................... 42
4.4.2
Setting cavity dumping time ............................................................................... 42
4.4.3
Setting pump current of oscillator ...................................................................... 43
4.4.4
Running RA at low repetition rates .................................................................... 43
4.4.5
“RA level” protection ......................................................................................... 44
4.5 5
Electrical and Environmental Specifications ............................................................... 3
Maintenance ............................................................................................................... 45
Control Software .............................................................................................................. 46 5.1
Installing PHAROS application and driver ............................................................... 46
5.2
Architecture of PHAROS application ........................................................................ 47
5.3
PHAROS application control windows ..................................................................... 49 4
5.3.1
“Connection” window ........................................................................................ 49
5.3.2
“Power Supply Controller” window ................................................................... 49
5.3.3
“Environment” window ...................................................................................... 50
5.3.4
“Osc./RA Bar Driver” window ........................................................................... 51
5.3.5
“Oscillator” window ........................................................................................... 51
5.3.6
“RA” window ..................................................................................................... 52
5.4 6
7
Remote Control Module ................................................................................................... 55 6.1
Oscillator control ....................................................................................................... 55
6.2
RA control.................................................................................................................. 57
6.3
LDD control ............................................................................................................... 58
Cables and connections .................................................................................................... 59 7.1
8
Protection of laser configuration parameters ............................................................. 53
Interlocks and “RA state” indication ......................................................................... 61
Timing Electronics Module (TEM) .................................................................................. 63 8.1
Principle of operation ................................................................................................. 66
8.2
Timing of laser control signals .................................................................................. 67
8.3
Pulse Picker operation modes .................................................................................... 69
8.4
External laser control interface .................................................................................. 70
8.5
Controlling TEM parameters ..................................................................................... 75
8.6
TEM failures/ warnings flags .................................................................................... 78
5
2 LASER SAFETY PHAROS is CLASS IV laser product that poses safety hazards if not used properly. Laser produces output beams that may cause devastating and permanent eye damage, may have sufficient energy to ignite materials, and may cause significant skin damage.
2.1 Optical safety. PHAROS emits infrared femtosecond pulses with average power of several watts. Each of the pump laser diode modules emits optical power of up to 60 W. Direct viewing of laser output beam or even specular reflection from polished surfaces can cause instantaneous and permanent eye damage and/or possible blindness. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ Avoid viewing the beam and specular reflections. Wear protective eyewear at all times when aligning and operating PHAROS. Make sure that your protective glasses cover all the wavelengths emitted by laser! ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ PHAROS beams are powerful enough to burn skin, clothing or paint. Laser beam can ignite substances in its path even at some distance. It also can damage light sensitive elements such as video cameras, photodiodes, etc. For this reasons, and other, user is advised to follow the precautions below: -
Never look directly into the light source or to scattered laser light from any reflective surface.
-
Wear protective eyewear at all times; choose protective eyewear depending on wavelength and intensity of the radiation, conditions of use, and visual function required.
-
Maintain experimental set-ups below eye level.
-
Set up energy absorbing targets and shields preventing unnecessary reflections or scattering.
-
Maintain a high ambient light level in laser operational area. This keeps the eye’s pupils constricted, thus reducing the possibility of eye damage.
-
Avoid blocking the output beam or its reflection with any part of your body. The intensity of beam can easily cause skin burns or ignite clothing.
-
Extreme caution must be exercised when using volatile solvents in the vicinity of laser. 6
-
Limit laser access only to qualified users who are familiar with laser safety practices and aware of dangers involved.
-
Use the laser in a closed room. Laser light remains collimated over long distances and therefore presents potential hazard if not confined.
-
Post warning signs near the laser operation area.
2.2 Electrical safety Hazardous voltages are present in the PHAROS laser head and power supply units. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬ -
Never remove the access covers of power supply and laser electro-optical units unless power supply is switched off and disconnected from the mains. Voltages present on these components present safety hazard, which could result in personal injury or death.
-
Do not connect or disconnect any cables with power supply turned on.
-
Any grounding interruption outside or within PHAROS system will pose an electrical shock hazard and could make the apparatus inoperative.
▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
Description of all PHAROS labels is presented in a table and figures below.
Table 2-1 Description of PHAROS labels
No.
Label
Description
1.
Manufacturer identification label is located on the end panel of the laser.
2.
Product identification label is located on the end panel of the laser.
7
3.
Warning logotype is located on the end panel of the laser. Depending on the device model actual radiation pulse energy and duration are recorded on label.
4.
Aperture label is located above the system aperture on a front panel of the laser. Depending on the device model actual radiation pulse energy and duration are recorded on label.
5.
Aperture label is located below the system aperture on a front panel of the laser.
6.
Product certification label is located on the end panel of the laser.
7.
Ground contact label is located on the end panel of the laser.
8.
Warning label is located on the top cover of the power supply.
9.
Product identification label is located on the end panel of the power supply.
8
3
1 6 7
2
Fig. 2-2 Location of labels on the end panel of PHAROS laser head. Label description is given in Table 2-1
4 5 Fig. 2-1 Location of labels on front panel of PHAROS laser head. Label description is given in Table 2-1.
9
8
9 Fig. 2-3 Location of labels on the end panel of PHAROS power supply. Label description is given in Table 2-1.
10
3 SYSTEM DESCRIPTION AND SPECIFICATIONS
3.1 PHAROS configuration PHAROS is a high repetition rate femtosecond laser system based on chirped pulse amplification (CPA) technique, which uses directly diode-pumped Yb:KGW (ytterbium doped potassium gadolinium tungstate) as active medium. Description of a typical CPA system can be found in books covering topics on femtosecond lasers (e.g., W.Koechner, Solid State Laser Engineering, Springer-Verlag, NY; J.C. Diels and W. Rudolph, Ultrashort laser pulse phenomena,
Academic
Press,
NY;
or
on
the
internet
http://www.rp-
photonics.com/chirped_pulse_amplification.html). The PHAROS laser head comprises of Kerr lens mode-locked Oscillator (OSC), Regenerative Amplifier (RA) and Stretcher-Compressor (S-C) units (see Fig. 3-1). The full system also incorporates an optional Remote Control Module (Fig. 3-1 (b)), power supply for laser diodes (Fig. 3-2) and appropriate water chiller that removes excess heat from the operating system, as well as stabilizes laser body temperature. PHAROS operation is automatically controlled by driving electronics and operating parameters can be adjusted from Remote Control Module or external PC that is linked via USB interface. Dedicated PC software and well developed library of commands are also included. As an option, PHAROS system can also include an electo-optical Pulse Picker for output pulse control and contrast enhancement and/or motorised delay line for automated Compresor lenght ajustment.
11
(a)
(b) Fig. 3-1 PHAROS laser head: (a) OEM version, (b) with external enclosure.
12
Fig. 3-2 PHAROS power supply unit.
13
3.2 Oscillator The oscillator (OSC) employs a cavity with chirped mirrors and a prism pair that is used for fine adjustment of group velocity dispersion. Yb:KGW crystal is end pumped by high brightness laser diode module. Generation of femtosecond pulses is ensured by Kerr lens modelocking, which is induced by perturbing the cavity length. Once started, the modelocking usually sustains throughout the days and is immune to minor mechanical impact. Repetition rate of oscillator pulses is 76 MHz, while typical output power is in the range of 6001200 mW. Spectral bandwidth is within 16-20 nm (FWHM) and yields corresponding pulse duration of ~70-90 fs. The OSC output power can be actively stabilized by power lock function. An electronic feed-back loop ensures compensation of the output power drift by changing the pump diode current.
3.3 Stretcher/compressor Stretcher and compressor of the PHAROS system employ transmission diffraction grating and both are enclosed in the same housing. By changing the compressor length it is possible to tune the output pulse duration from a minimal value, which is laser model dependent, to a maximum one of about 10 ps (limited by the length of translation stage used in compressor). Compressor length adjustment in the standard PHAROS system is manual; whilst a computer controlled motorized stage can be installed as an option.
3.4 Regenerative amplifier Regenerative amplifier incorporates a Yb:KGW crystal that is pumped by one or two continuous wave (CW) pump modules. A single BBO (beta-BaB2O4) Pockels cell within the amplifier cavity is used to inject the seed and dump the amplified pulse. Any pump light modulations or fast changes in the repetition rate are not allowed within the CW pumped regenerative amplifiers. These fast perturbations may cause optical damage of the cavity components due to uncontrolled increase in pulse energy. An optional external pulse picker (PP), which is based on the second Pockels cell, can be used to control every pulse from the RA output. The pulse picker is installed in the same housing of regenerative amplifier within the beam path to the compressor module. The high voltage (HV) switches together with HV supplies for both Pockels cells are located outside of the housing as separate modules. In high repetition rate (500 kHz) PHAROS systems a more powerful HV 14
supply comes as a separate unit (19” standard) in the same rack as power supply of laser diode bars. CW pumped regenerative amplifiers have a specific non-saturated form of pulse train in the RA cavity (Fig. 3-3). The form of the train is determined by CW pump and relatively low gain of amplifier at repetition rates higher than inverse life-time of upper level of a gain medium (0.35 ms for Yb:KGW crystal). A steady-state condition for inversion and pulse energy requires relatively early cavity dumping in order to sustain sufficiently high gain for the following (next) pulse. CW pumped amplifiers have three typical regimes of operation which are listed in Table 3-1. CW pumped regenerative amplifier is a highly non-linear system, which can lead to output pulse energy bistability at repetition rates from 5 kHz to 40 kHz. The bistabily can be detected by monitoring the output photodiode signal with an oscilloscope. It manifests as two alternating in time output pulse energies. This phenomenon can be eliminated by reducing the cavity dumping time.
15
Regimes of RA operation Table 3-1
Repetition rate <5 kHz
Pulse energy
Peculiarities of RA operation
Warnings
0.4-1.0 mJ
Do not exceed maximum pulse energy (too high pump current, too long cavity delay time)
5-40 kHz
100-400 J
- High gain - Increased risk of optical damage due to high pulse energy - Possible self-phase modulation - Moderate gain - Bistability at long cavity damping times
>40 kHz
< 100 J
- Low gain - Low pulse energy - high output power
Check for bistabilty. Reduce delay time or pump current to avoid bistability. Too high output power can lead to thermal lensing and degradation of beam quality.
16
Fig. 3-3 Typical pulse train in the cavity of CW pumped regenerative amplifier.
Note: NO SATURATION of the train is observed! CAUTION! DO NOT
TRY TO SATURATE THE PULSE TRAIN IN THE
CAVITY DELAY TIME .
THIS
RA
CAVITY BY INCREASING
MAY LEAD TO SELF -PHASE MODULATION OF LASER
PULSE AND OPTICAL DAMAGE OF CAVITY COMPONENTS .
CAUTION! BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN OF A PULSE IN THE CAVITY . IT APPEARS AS TWO TRAINS WITH DIFFERENT AMPLITUDES . CAUTION! IN ORDER
TO OBSERVE BISTABILTY OF OPTICAL PULSES , TRIGGERING OF AN
OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.
USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE .
17
3.5 Mechanical design Laser head of PHAROS system has a multi-module structure (Fig. 3-4 ) that includes: - Oscillator (OSC), - Regenerative Amplifier (RA), - Stretcher/Compressor (S-C), - Timing Electronics Module (TEM), - High voltage supply for RA Pockels cell, - High voltage supply for PP Pockels cell (optional), - RA Pockels cell driver, - PP Pockels cell driver (optional). Bodies of oscillator, regenerative amplifier, stretcher/compressor and Pockels cell driver modules are water cooled, which leads to a good heat management in the system and ensures mechanical stability that is independent on environmental conditions. The most sensitive modules are fixed together using three point kinematic mounts, which reduces mechanical stress caused by thermal expansion and ensures robustness of the system.
18
3 4 1
5 2 7 6 8
Fig. 3-4 Mechanical design of PHAROS laser head.
1 - Oscillator 2 - Regenerative Amplifier 3 - Stretcher/Compressor 4 - Timing Electronics Module 5 - High Voltage supply for RA Pockels cell 6 - High Voltage supply for PP Pockels cell (optional) 7 - RA Pockels cell driver 8 - PP Pockels cell driver (optional)
19
3.5.1 Regenerative amplifier Monolithic block of regenerative amplifier (RA) body is the main support for other units of the laser head. It has two sections from two different sides: 1) section of the pump modules is situated from the side of oscillator and 2) section of the RA cavity is situated from the side of high voltage supplies. Stretcher/compressor of the system is attached to the front end of the RA body. Oscillator of the system is attached to the RA by a three point kinematic mount.
3.5.1.1 Fixing to an optical table PHAROS system is fixed to an optical table using three point kinematic mount with three cylindrical bearings, which eliminate mechanical deformations caused by difference in thermal expansion coefficients between optical table (typically made of steel) and aluminium body of the laser head. Six M6 screws are used to fix laser head to an optical table (see Fig. 3-5). OEM laser heads have three guiding points for parallel keys (6x6x20mm) on the legs that ensure precise positioning of laser head on to the base plate. This allows maintaining precise direction of laser beam after removal of the laser head.
CAUTION! NOTE,
THAT IF PARALLEL KEYS ARE USED BETWEEN LEGS AND BASE PLATES,
THERE IS AN INCREASED RISK FOR MECHANICAL SHOCK DURING THE PLACEMENT OF LASER HEAD .
BE CAREFUL WHILE LOCATING THE LASER HEAD IN TO CORRECT
POSITION .
20
Fig. 3-5 Bottom view of PHAROS laser head (OEM vesion). Fixing points are marked with arrows. Red arrows – M6 screws, brawn arrows – 6x6x20mm parallel keys.
Fig. 3-6 Bottom view of the PHAROS laser head (with external enclosure). Six fixing holes are marked with red arrows.
21
3.5.1.2 Connections All the connections to regenerative amplifier are presented in
Fig. 3-7.
10
9 6
5 4 8
7
2
1
3
Fig. 3-7 Connections to regenerative amplifier:
1 – Pump current of LD bars. 2 – Water from chiller (inlet to laser head), labeled. 3 – Water to chiller (outlet of laser head). 4 – Water from Pockels cell driver. 5 – Water to oscillator. 6 – Water from oscillator. 7 – Water to Stretcher/Compressor. 8 – Dry air/nitrogen to section of pump modules. 9 – Dry air/nitrogen to section of laser cavity. 10 – CAN bus connector under the cover.
22
3.5.1.3 Adjustment screws Micrometer screws for regenerative amplifier mirror adjustment are situated on the rear side of RA (see Fig. 3-8).
WARNING ! DO
NOT ADJUST MIRRORS OF THE REGENERATIVE AMPLIFIER WITHOUT
ADVICE OF AN AUTHORIZED REPRESENTATIVE . MISALIGNMENT
OF
THE
SYSTEM .
THIS MAY CAUSE COMPLETE
CONSULT
MANUFACTURER
OR
AUTHORIZED REPRESENTATIVE BEFORE ADJUSTING ANY MIRRORS .
8 1 3 2 4
7
6
5
Fig. 3-8 Micrometer screws for mirror adjustment of regenerative amplifier. 1 – Cavity mirror No.1, horizontal direction. 2 – Cavity mirror No.1, vert dir. 3 – Cavity mirror No.2, vert dir. 4 – Cavity mirror No.2, hor dir. 5 – Output folding mirror, vert dir. 6 – Output folding mirror, hor dir. 7 – Inspection window. 8 – Adjustment of seed direction to RA
23
3.5.1.4 Photodiodes Four photodiodes are used to monitor the performance of regenerative amplifier: 1. Internal power meter. Slow photodiode (bandwidth < 1 kHz) is used to monitor the output power. The photodiode is located in the RA section of pump modules. The signal of internal power meter is used by a controller of the system. The internal power meter cannot be calibrated for absolute output power measurements. It is used for relative measurements and output power stabilization. 2. RA level. Fast photodiode for monitoring pulse amplitude in the RA cavity. Signal of this photodiode is used by Timing Electronics Module (TEM) to limit the maximum pulse energy inside RA cavity, and thus protecting optical components from damage. The photodiode is located between the body of RA and Stretcher/Compressor. 3. RA train. Fast photodiode for monitoring pulse train in the RA cavity. The signal of this photodiode is delivered through the Timing Electronics Module to the output panel of TEM. The photodiode is located behind end mirror of the cavity of RA under the cover on top of RA (Fig. 3-9). 4. Output pulse. The photodiode is located within the housing of stretcher/compressor module. Signal of the photodiode is delivered through the Timing Electronics Module to the output panel.
Fig. 3-9 RA train photodiode is located under the cover (marked with black arrow).
24
3.5.2 Oscillator Oscillator (OSC) module is milled from a single monolithic aluminium block that together with its water cooled body ensures stable and robust operation. This OSC housing has two separate sections: 1) cavity section that is from the side of regenerative amplifier (RA) and 2) pump module section that is on the opposite side. Detector module, which includes photodiode for OSC power monitoring, is attached to the front side of the oscillator.
3.5.2.1 Fixing Oscillator is fixed to the RA body by three point kinematic mount (Fig. 3-10Error! Reference source not found.) which includes two cylindrical bearings. The use of bearings servers two purposes: 1) Elimination of possible deformations that may arise between RA and oscillator housings. 2) Making the oscillator conveniently accessible (by lifting it up) for service purposes without dismounting it from the RA body.
Fig. 3-10 Oscillator fixing points (indicated with red arrows)
CAUTION ! THEN
OSCILLATOR IS FIXED ONLY ON TWO UPPER POINTS , THERE IS A RISK FOR
MECHANICAL IMPACT WITH THE THIRD (LOWER) FIXING POINT .
T HIS
MAY CAUSE
MISALIGNMENT OF OSCILLATOR CAVITY.
25
3.5.2.2 Connections
6 5 4 3 2 1
Fig. 3-11 Connections to Oscillator.
1 – Pump current of LD bars. 2 – Water inlet to oscillator. 3 – Water outlet from oscillator. 4 – Dry air/nitrogen to pump section. 5 – Dry air/nitrogen to laser cavity section. 6 – Inspection window.
26
3.5.2.3 Adjustment screws and signal connections on front panel of oscillator Adjustment micro-screws of output mirror and end mirror of oscillator are situated on the front side of oscillator (see
Fig. 3-12).
6 2 5 4
10 9
3
11
8 7 1 Fig. 3-12 Front side of oscillator with removed Detector module.
1- Output window of oscillator. 2- End mirror window. 3- Micrometer screw for adjustment of output mirror (horizontal direction). 4- Micrometer screw for adjustment of output mirror (vertical direction). 5- Micrometer screw for adjustment of end mirror (vertical direction). 6- Micrometer screw for adjustment of end mirror (horizontal direction).. 7- CAN bus connection. 8- DC supply for fast photodiodes of Detector Module. 9- Connector of internal power meter. 10- not connected
27
3.5.2.4 Photodiodes Four photodiodes are used to measure signals of oscillator, they are listed in Table 3-2. Three of the diodes are situated in the Detector module which is attached to front side of the oscillator (Fig. 3-13). The fourth photodiode “Narrow bandwidth” is located in the stretcher/compressor housing and monitors the spectral bandwidth of oscillator. Signal of one fast photodiode is used to monitor pulse train in the cavity of oscillator. signal of this photodiode is coupled directly into an output panel of the Timing Electronics Module (PD OSC). Signal of the second fast photodiode is used for triggering of Timing Electronics Module as a clock for whole system. Both fast photodiodes detect leakage of an optical pulse through the end mirror of the oscillator (arrow No.2 on
Fig. 3-12). The third slow photodiode monitors output power of the oscillator. signal of this photodiode is used by an internal controller. The Narrow Bandwidth photodiode is installed in the stretcher where the spectrum of oscillator is spread spatially. Signal of this photodiode is used to recognize whether oscillator is mode-locked. Controller of the system generates a failure message if the signal of “Narrow bandwidth” photodiode is too low. The signal of this photodiode is used to find optimal pump current for the oscillator. A presence of CW component in the output of oscillator is detected using the signal of this photodiode.
Photodiodes of oscillator
Photodiode
Table 3-2
Location
Bandwidth
1.
For Pulse Train
Detector Module
300 MHz
2.
Clock for TEM
Detector Module
300MHz
3.
Internal power meter
Detector Module
<1kHz
4.
Narrow bandwidth
Stretcher/compressor
1MHz
28
Osc sync Osc PD
Fig. 3-13 Front side of the oscillator with the Detector module. Osc. sync connected to TEM, Osc. PD connected to external panel.
29
3.5.3 Stretcher/compressor Stretcher of the PHAROS system is designed to produce a temporal pulse stretching using positive dispersion diffraction grating setup. Output of the stretcher is seeded into regenerative amplifier for amplification and subsequent compression. Compressor of the Pharos system is built into the same housing as the stretcher and shares the same diffraction grating. By changing the compressor length it is possible to induce negative or positive pulse chirp and consequently change the output pulse duration. PHAROS with motorized translation stage this can be done from the PHAROS software, while in PHAROS with manual compressor length adjustment a micrometer screw is located under the cover 1 (see Fig. 3-14). In order to adjust the compressor length it is necessary to remove the cover (1 in Fig. 3-14) and turn the micrometer screw using hex key. Clockwise rotation produces a positive chirp whilst counterclockwise yields a negative one.
CAUTION! ADJUSTMENT
OF COMPRESSOR ’S THIRD ORDER DISPERSION
FIG. 3-15) REQUIRES SPECIAL
SKILLS.
CONTACT
(OPENING 3,
MANUFACTURER OR YOUR
AUTHORIZED REPRESENTATIVE FOR INSTRUCTIONS.
30
3
1 2 Fig. 3-14 Stretcher/compressor of PHAROS system. Rear view.
1- Opening for manual adjustment of the length of the compressor (adjustment of pulse duration, Second Order Dispersion). Remove the cover for adjustment. 2- Water connection for temperature stabilization. 3- Signal connections: NB – Narrow Bandwidth. Monitors bandwidth of the oscillator spectrum . LVL – RA level. Monitors pulse energy in the cavity of RA. PD – Output Photodiode. Monitors output pulse energy.
4
2
1
3
Fig. 3-15 Stretcher/compressor of PHAROS system. Front view.
1234-
Output window. Micrometer screw of folding output mirror. Opening for adjustment of Third Order Dispersion (TOD). Shutter of the seed light. O - opened, C – closed.
31
3.5.4 Pockels cell driver and High voltage supply For removal of HV supply or Pockels cell drivers from the RA do following: 1. Release 4 screws from the top of HV supply modules (see 1 in Error! Not a valid ookmark self-reference.). 2. Pull and rotate by 90deg a plastic chuck (see 2 in Error! Not a valid bookmark elf-reference.). 3. Detach driver and HV supply. 4. Disconnect water tubes and cable connections. Back side of the Pockels cell drivers and HV supplies with all the connections are shown in Fig. 3-17.
CAUTION! THERE ARE SPECIAL SHIELDING METAL RINGS BETWEEN DO NOT FORGET TO PUT THEM DURING ASSEMBLING. WARNING! DO
NOT TRANSPOSE TIMING CABLES NEITHER ON
NOR
TIMING ELECTRONICS MODULE
SIDE .
T HE
THE DRIVER AND
POCKELS
RA.
CELL DRIVER SIDE
TRANSPOSE OF TIMING CABLES
CAN LEAD TO UNCONTROLLED AMPLIFICATION OF AN OPTICAL PULSE IN THE CAVITY OF
RA
AND AS A CONSEQUENCE IRREVERSIBLE OPTICAL DAMAGE OF
OPTICAL COMPONENTS OF THE LASER CAVITY .
WARNING! DO
NOT START THE LASER IF TIMING CABLES ARE NOT CONNECTED .
THIS
CAN
LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE LASER CAVITY .
WARNING! DO NOT START THE LASER IF POCKELS CELL DRIVERS ARE GROUNDED . THIS CAN LEAD TO IRREVERSIBLE OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE LASER CAVITY .
32
1
2
Fig. 3-16. Removal of Pockels cell drivers and High voltage supplies.
4 2
1
2
3 Fig. 3-17 Connection of Pockels cell drivers and HV supplies to RA. View from the side of RA.
1234-
HV connectors to Pockels cells. Timing connectors ON/OFF. Water connection. CAN bus to HV supply.
33
3.6 Specifications Due to continuous product improvement program, specifications may change without notice. PHAROS-4W
PHAROS-6W
PHAROS-SP
1030±3
1030±3
1030±3
4
61
5
1-2002
1-2002
1-2002
Typical pulse duration*, fs
280
280
180
Maximum pulse energy, mJ
0.2
0.2
1.0
<0.5%
<0.5%
<0.5%
Oscillator pulse duration, fs
<90
<90
<90
Oscillator output power, W
>0.63
>0.63
>0.63
764
764
764
Parameter Central wavelength, nm Average output power, W Repetition rate, kHz
Stability of pulse energy, STD
Oscillator repetition rate, MHz Weight of OEM laser head
34kg
Weight of laser head with external enclosure
42kg
Weight of power supply
13kg
Weight of chiller (approx.)
32kg or 40kg
* defined at FWHM and slightly varies with repetition rate 1
Extendable up to 10 W Versions with higher repetition rates (up to 1 MHz) are available. 3 High power oscillator (>2 W) can be integrated then partial oscillator output is necessary. 4 Customized repetition rates and/or active stabilization of the cavity length are available on request. 2
Optional accessories - Pulse picker for “pulse-on-demand” operation. - Stepper motor equipped translator for computer controlled adjustment of compressor length (maximum pulse duration ca. 10 ps). -
34
4 Operation and maintenance of the system 4.1 Installation CAUTION! YOUR PHAROS
LASER
WAS
PACKED
WITH
GREAT
CARE ,
AND
IT ’S
CONTAINER WAS INSPECTED PRIOR TO SHIPMENT. IF ANY MAJOR DAMAGE WAS NOTICED AT THE TIME OF RECEIPT (HOLES IN THE CONTAINER, WATER LEAK, CRUSHING, ETC.) PLEASE NOTIFY THE CARRIER AND MANUFACTURER .
CAUTION! IF
LASER WAS TRANSPORTED IN COLD WEATHER CONDITIONS , KEEP IT IN
TRANSPORTATION BOXES FOR AT LEAST
6
HOURS AT ROOM TEMPERATURE
IN ORDER TO PREVENT POSSIBLE WATER CONDENSATION ON THE SENSITIVE COMPONENTS OF THE LASER AFTER AN OPENING .
LASER
HEAD IS
HERMETICALLY SEALED IN PLASTIC BOX .
CAUTION! IT
IS RECOMMENDED THAT YOU WAIT FOR YOUR
REPRESENTATIVE TO UNPACK YOUR SYSTEM .
IN
LIGHT CONVERSION
NO EVENT SHOULD YOU
ATTEMPT TO INSTALL THE LASER YOURSELF WITHOUT PRIOR AGREEMENT OF LIGHT CONVERSION LTD .
ANY UNAUTHORIZED ACTION WILL VOID YOUR
WARRANTY AND YOU WILL BE CHARGED FOR THE REPAIR OF ANY RESULTED DAMAGE .
1. Carefully remove laser head, power supply and chiller from the transportation boxes. Retain these boxes for possible transportation in the future. 2. Remove humidity absorbers from the laser and power supply. 3. Remove a tin shell and metal sheet from the bottom of laser head (for OEM laser heads only). 4.
Place laser head on the optical table and fix it using appropriate screws. Fixing of the OEM laser head is shown in Fig. 3-5, while fixing of the laser head with external enclosure is shown in Fig. 3-6. Note that you’ll need to remove the cover of PHAROS external enclosure, consult Fig. 4-1.
WARNING! AVOID HARSH MECHANICAL IMPACTS WHEN PLACING LASER HEAD ON THE OPTICAL TABLE . THIS CAN CAUSE MISALIGNMENT OF THE LASER CAVITY.
35
2. Thrust forward
3. Raise up
1. Bend the fixer Fig. 4-1. Cover removal in the case of laser with external enclosure.
WATER OUTLET WATER INLET Fig. 4-2. Water inlet and outlet of the PHAROS laser head.
36
5. Connect laser diode power cable (4 high current cables) from power supply to laser head. 6. Connect control cables from Power supply to Remote Control Module and from Power supply to laser head. 7. If you intend to control laser operation from a personal computer, connect computer and power supply via USB cable and install the PHAROS software. WARNING! PHAROS
USB
CABLE .
PHAROS
POWER
LASER MUST BE GROUNDED BEFORE CONNECTING
IMPROPER
GROUNDING CAN DAMAGE COMPUTER AND/OR
SUPPLY .
8. Connect water tubes from chiller to laser head. Water inlet to laser head is marked with red label (see Fig. 4-2). CAUTION! THE
DIRECTION OF COOLING WATER FLOW IS IMPORTANT FOR PROPER
SYSTEM OPERATION . FLOW DIRECTION .
CONNECT
INCORRECT AND POSSIBLE DAMAGE .
THE HOSES DILIGENTLY WITH PROPER
FLOW MAY CAUSE UNSTABLE OPERATION
CAUTION! CHILLER
SHOULD BE LOCATED SO THAT THE WARM AIR EXHAUST AT THE
BACK PANEL WOULD NOT BLOW INTO THE
POWER
SUPPLY UNIT AND VICE
VERSA .
9. Fill the chiller with distilled water. Note that manufacturer do not recommend using any special water additives to preventing corrosion and/or growth of algae. Consult the manufacturer before using any water additive. CAUTION! USE
ONLY
STEAM-DISTILLED
WATER.
THE
USE OF HIGHLY DE -IONIZED
WATER MAY CAUSE CORROSION DAMAGE .
10. Connect the mains cables for chiller and power supply. 11. Check connections of other cables. See Chapter 7 of this Manual. 12. Switch-on the chiller and check for water leakage. Add water if necessary. The temperature of cooling water must be set to room temperature at the beginning. Then it must be changed slowly (1degC in 5min.) to operating temperature 20-23 degC defined in the Factory test certificate. Water flow from chiller should not exceed
37
3 l/min and water pressure should be <3 bars. It is advised to use the same values as in the Factory test certificate. Read chiller manual for adjustment of flow and pressure. CAUTION! FAST
CHANGE OF LASER HEAD TEMPERATURE MAY CAUSE MISALIGNMENT
OF THE SYSTEM .
13. Turn key to position “Laser ON” to start pump laser diodes. Check for pump currents of the oscillator and amplifier in Factory test certificate. Change the pump currents if necessary. 14. Warm-up the laser for 5-10min. Output power of oscillator in CW regime must reach value stated in Factory test certificate (100-400mW).
Starting oscillator 1. Connect an oscilloscope to “PD OSC” BNC connector for observation of pulse train in the oscillator. 2. Press “Oscillator” “Start” button on Remote Control Module (RCM) or appropriate button on the Pharos software. This moves prism inside the cavity of oscillator to initiate mode-locking. “Running” indication on the “Status” line of RCM must appear (electronics detects 76MHz frequency in the signal of photodiode). If oscillator doesn’t start, increase or decrease pump current and try to start oscillator again. 3. To optimize performance of the oscillator use a signal of the “Narrow Spectrum”. photodiode(RCM: Osc, NB detector; Pharos software: “RA”, “Narrow Spectrum”). First measure interval of pump currents at which signal of “Seed control” photodiode changes from its maximum value (A1, point there CW component in optical spectrum appears) to its minimum value (A2, laser jumps from mode-locking to CW regime). Set the pump current such that signal of “Narrow Bandwidth” photodiode acquires its average value ((A1-A2)/2). 4. For long term stability this value of the output power can be locked using “Power lock function” which activates feedback loop between an internal power meter reading and pump diode current.
38
Starting regenerative amplifier Before starting RA check the following: a) RA delay doesn’t exceed the value defined in the Factory test certificate. b) RA repetition rate is high enough (>75kHz). Risk of optical damage of optical components is reduced at high repetition rates and short RA delays. c) Pump current of RA doesn’t exceed the value defined in the Factory test certificate.
1) Connect a cable from oscilloscope (>300MHz bandwidth or 2Giga-samples/sec, time-base 100-200ns/div, 50Ω input impedance) to “Scope” BNC connector on Timing Electronics Module for triggering of an oscilloscope. Use connection “RA” for monitoring pulse train in the cavity. 2) Install optical power meter on the output of laser. 3) Start the amplifier by pressing “Start” and “PP closed” buttons.
The following parameters of the system must be checked after an installation: -
Mode-locked range of oscillator.
-
Mode-lock staring range of oscillator.
-
Output power of the system (pump current, cavity delay time and repetition rate should be the same as indicated in Factory test certificate)
-
Output power of the system in Q-switched regime with closed seed light (pump current, cavity delay time and repetition rate should be the same as indicated in Factory test certificate).
39
4.2 Quick start When laser is installed and properly adjusted starting procedures is described in Table 4-1. Table 4-1
Action 1.
2. 3.
4.
5.
6.
7
Position
Result
Switch the key to position Power supply “Laser on”
Switches on: - chiller, - HV supply for Pockels cells, - pump current of oscillator - pump current of RA Wait 10min Heats up pump module, sets proper pump wavelength Press button “Start” in window Remote Control Initiates mode-locking in the of oscillator Module or software oscillator on computer Press button “Lock” in Remote Control Locks the output power of the window of oscillator Module or software oscillator using a signal of on computer internal power meter. Set the required parameters of Remote Control the regenerative amplifier: Module or software - pump current, on computer - cavity delay time, - repetition rate Press “Start” in window of RA Remote Control Starts operation of RA Module or software on computer Press “PP closed” in window Remote Control Activates pulse picker and of RA Module or software directs RA output light to the on computer output aperture of the laser
40
4.3 Switching-off Switching-off procedures are listed in the Table 4-2 Table 4-2
Action 1.
2.
Position
Operation
Press button “Stop”
Remote Control Stops the regenerative Module or computer, amplifier RA Turn the key on Power supply Power supply Slowly reduces pump currents to position “Power off” for oscillator and amplifier diodes and switches-off the system.
CAUTION! SWITCHING -OFF
OF THE LASER TAKES APPROXIMATELY ONE MINUTE , DUE
TO GRADUAL DECREASE OF PUMP CURRENT . ONLY AFTER THE
T HE MAINS ARE SWITCHED OFF
RA AND OSC CURRENTS WERE REDUCED TO ZERO.
41
4.4 Setting parameters 4.4.1 Setting pump current regenerative amplifier Use Factory test certificate to determine required pump current of laser diode bars of regenerative amplifier. The pump current may slightly vary due to the possible misalignments in the system.
CAUTION! IT
IS ADVISED NOT TO EXCEED
50 A
PUMP CURRENT .
THIS
MAY LEAD TO THE
REDUCTION OF PUMP BAR LIFETIME AND DETERIORATION OF OUTPUT BEAM PROFILE DUE TO THERMAL LENSING WITHIN LASER CRYSTAL .
4.4.2 Setting cavity dumping time Use Factory test certificate to determine required cavity dumping time of regenerative amplifier. Output pulse duration depends on the dumping time due to a different optical path length in the crystals (laser crystal and Pockels cell) of the cavity. Set optimal compressor length for different dumping times. Read Chapter 4.4.4 for Running RA at low repetition rates. See Fig. 3-3 for typical train of optical pulse in a cavity of RA. CAUTION! DO NOT
TRY TO SATURATE THE TRAIN OF OPTICAL PULSE IN THE CAVITY OF
BY INCREASING CAVITY DELAY TIME .
THIS
RA
MAY LEAD TO SELF MODULATION OF
AN OPTICAL PULSE AND OPTICAL DAMAGE OF OPTICAL COMPONENTS OF THE CAVITY OF REGENERATIVE AMPLIFIER .
CAUTION! BISTABILITY OF THE OUTPUT PULSE CAN BE OBSERVED ON THE TRAIN IN THE CAVITY . IT APPEARS AS TRAIN WITH CHANGING AMPLITUDE . CAUTION! TO
OBSERVE
BISTABILTY
OF
THE
OPTICAL
PULSE ,
OF A PULSE
TRIGGERING
OF
AN
OSCILLOSCOPE MUST ENSURE VISUALIZATION OF TWO ADJACENT PULSES.
USE PROPER OSCILLOSCOPE WITH REQUIRED FUNCTION AVAILABLE .
42
4.4.3 Setting pump current of oscillator Use Factory test certificate to determine required pump current of oscillator. Due to the possible misalignment of the oscillator required pump current may be slightly differ from that one indicated in the Factory test certificate. To optimize performance of the oscillator use a signal of the “Narrow Spectrum”. photodiode(RCM: Osc, NB detector; Pharos software: “RA”, “Narrow Spectrum”). First measure interval of pump currents at which signal of “Seed control” photodiode changes from its maximum value (A1, point there CW component in optical spectrum appears) to its minimum value (A2, laser jumps from mode-locking to CW regime). Set the pump current such that signal of “Narrow Bandwidth” photodiode acquires its average value ((A1-A2)/2).
4.4.4 Running RA at low repetition rates Risk of damaging of laser crystal by high energy optical pulse increases if laser is operated at low repetition rates (<20kHz). At the low repetition rates active medium of the laser has enough time to accumulate too much of energy in the upper level. This leads to increase in gain and can lead to optical damage of laser crystal. This problem is also inherent for starting the CW pumped regenerative amplifiers, therefore feature of “Soft Start” is installed in the hardware of timing electronics. “Soft Start” feature means that at a start moment cavity dumping time of the RA is reduced to its minimum value (<150ns) and then is increased gradually to a set value during about 1second.
Starting laser at low repetition rates: 1. Install energy or power meter at the output of PHAROS and an oscilloscope for monitoring the pulse train in the cavity of RA; 2. Reduce pump current of RA to 25-28A; 3. Set a proper cavity delay time from Pharos test certificate 4. Set a required repetition rate; 5. Start RA; 6. Slowly increase pump current of RA to the level of required output pulse energy. DO NOT EXCEED MAXIMUM PULSE ENERGY ALLOWED FOR PARTICULAR SYSTEM (1mJ, 600J or 200J pulse energies are allowed for different Pharos 43
systems). When the proper pump current is found the RA can be stopped and started at the same pump current; 7. Check for bistability of output pulse. Bistabilty is a nonlinear phenomenon inherent for CW pumped regenerative amplifiers as highly nonlinear systems. The bistability can be observed on oscilloscope as appearance of two different pulse energies of adjacent output pulses. This occurs when the pulse energy is high enough to remove a great part of inversion accumulated in a laser crystal in a single pass so the pulse energy becomes influenced by energy of its predecessor. For stable operation of the laser the bistability must be eliminated by decreasing of cavity delay time in regenerative amplifier. It is recommended to set the delay time shorter by one round trip from the “bistable” delay time.
4.4.5 “RA level” protection PHAROS has two level protection system against high optical pulse energy which can damage optical components of the cavity. A dedicated photodiode is installed behind one of the mirrors of the cavity of regenerative amplifier for monitoring pulse amplitude of the optical pulse in the cavity. Timing Electronics Module continuously measures amplitude of the optical pulse. Two level protection against high pulse energy is implemented in Pharos system: RA level WARRNING – pulse reaches dangerous energy. The system sends warning message, but doesn’t stop the amplifier. RA level FAIL - pulse energy is too high. The system sends warning message and stops the amplifier.
WARNING! THE “RA
LEVEL ” PROTECTION SYSTEM IS NOT FAST ENOUGH TO STOP AN
AMPLIFICATION OF A PULSE DURING A SINGLE AMPLIFICATION CYCLE .
DO
NOT START REGENERATIVE AMPLIFIER AT HIGH PUMP CURRENT AND LONG CAVITY DUMPING TIME AT LOW REPETITION RATES (SEE
TABLE 3-1
FOR
DETAILS ).
44
4.5 Maintenance For every day work it is important to prevent formation of algae in water of cooling system. Appearance of algae in cooling system can lead to formation of plugs in critical places, this cause overheating of laser crystal, softening of water tubes and possibly swamping and damaging of the laser. To prevent formation of algae plugs it is important to change cooling water once per three month. The cooling system of the laser must be rinsed with clean water two times during the replacement of the water. Water filter of the cooling system is situated on a back panel of the chiller. Remove the filter and wash it carefully. The filter must be changed once per year. For maintenance of the chiller read manual of the chiller. CAUTION! USE
ONLY
STEAM-DISTILLED
WATER.
WATER MAY CAUSE CORROSION
THE USE OF HIGHLY DE -IONIZED DAMAGE . MANUFACTURER DOES NOT
RECOMMEND USING ANY SPECIAL ADDITIVES TO WATER FOR PREVENTING THE CORROSION AND THE GROWTH OF ALGAE .
CONSULT MANUFACTURER BEFORE USING ANY ADDITIVE TO COOLING WATER. DIFFERENT METALS ARE USED IN THE COOLING SYSTEM AND THE WATER ADDITIVES CAN CAUSE DAMAGE OF THE COOLING SYSTEM .
Variation of the room temperature should not exceed ±5degC for stable operation of the laser. Recommended room temperature is 22±2deg. Each Pharos system is aligned and optimized for defined cooling water temperature, usually 20degC or 23 degC. Operation at different water temperature can cause a misalignment or poor performance of the system. CAUTION! IT
IS IMPORTANT TO PREVENT WATER CONDENSATION ON THE COOLED
COMPONENTS OF THE LASER AT HIGH HUMIDITY AND TEMPERATURE IN A ROOM .
USE A PSYCHROMETRIC CHART (e.g., http://en.wikipedia.org/wiki/Psychrometrics) TO CALCULATE A DEW POINT IN YOUR LABORATORY . THE DEW POINT SHOULD NOT BE HIGHER THAN WATER TEMPERATURE FROM A CHILLER . DO NOT USE LASER IF THERE IS A RISK OF WATER CONDENSATION . C ONSULT MANUFACTURER FOR OPTIMAL REGIME OF LASER OPERATION AT HIGH HUMIDITY CONDITIONS. Power supply of Pharos system has air filter on the fan. The air filter must be checked in every three months and cleaned if necessary.
45
5 Control Software Full control of PHAROS parameters is accessible from PHAROS computer application. This application also can be used for PHAROS state monitoring, visualization and logging. Computer connects to PHAROS power supply over USB bus CAUTION! PHAROS
LASER MUST BE GROUNDED BEFORE CONNECTING
PC. IMPROPER
GROUNDING CAN DAMAGE COMPUTER OR
USB
CABLE TO
PHAROS
POWER
SUPPLY .
5.1 Installing PHAROS application and driver Installation package of PHAROS application is provided on CD together with laser documentation. The latest version of software can be downloaded from PHAROS support site http://pharos.lightcon.com (registration required). PHAROS application is supported on Microsoft Windows XP and Microsoft Windows Vista 32-bits operation systems. The only requirement for a PC is one free USB socket. To install software to PC insert installation CD into CD drive or run Setup.exe file and follow installation instructions. After software is installed, connect PHAROS power supply to the mains (There is no need to turn power supply off), plug USB cable to computer and PHAROS power supply. Windows will detect a new hardware. On Windows Vista select: “Locate and install software” “I don’t have the disc. Show me other options” “Browse my computer for driver software”. On Windows XP select: “No, not his time” “Install from a list or specific location” “Include this location in the search”. Then
browse
to
PHAROS
installation
directory\Driver
(typically
C:\Program
Files\PHAROS\Driver) and select kmdf_lc_usb.inf file to install. If driver is installed successfully start PHAROS application. It will connect to the laser automatically. If laser was not connected while starting application, button “Connect” must be pressed in “Connection” window.
46
5.2 Architecture of PHAROS application PHAROS application is designed as set of modeless windows. Every window contains controls and indicators grouped by functions or PHAROS system subunits. Windows can be showed or hidden using menu option View Window name. If PC monitor resolution is low, user can choose to hide unnecessary windows. All windows can be docked inside main application window or docked and tabbed inside each other to save display space and design ergonomic control environment. To dock or tab window move mouse to the caption area, press left mouse button and move window to required position. Graphical menu with docking/tabbing options will appear near the mouse cursor.
Fig 5-1. PHAROS application
Additional graph windows can be added if long term monitoring of certain parameters is required. To add graph windows press button
or select menu Graphs Add New
Graph. Dialog with selection of graphs will appear and can be used to select parameters that must be displayed in graphs.
Fig 5-2. Example of graph window
Parameters and positions of graph windows are saved when PHAROS application shuts down and are restored on the next start of software. Toolbar on top of graph window provides buttons for these operations: 47
Access graph properties Auto scale of graph
,
,
Save data points to ASCII file Save graph as image to file
, ,
Enable real-time backup graph data to file Clear all collected data
,
,
Change time scale of graph from 1 minute to 64 hours
,
Standard normalized deviation of data displayed on graph. “Graph Properties” window allow to customize graph colors and fonts, type and size of for data points and lines, vertical axis range, to enable/ disable auto scaling and logarithmic vertical scale.
Fig 5-3. Example of “Graph Properties” window
48
5.3 PHAROS application control windows This chapter briefly describes main functions of PHAROS application control windows. List of all windows can be displayed expanding menu option View.
5.3.1 “Connection” window A “Connection” window is used to select PHAROS device (if more than one laser is connected to the same computer) and connect/disconnect to the laser. If only one laser is connected to the computer, power supply is connected to the mains and USB cable is plugged to computer and PHAROS power supply, application will connect to the laser automatically. Also there is no need to disconnect while shutting down application.
Fig 5-4 "Connection" window
5.3.2 “Power Supply Controller” window A “Power supply Controller” window can be used to switch on and off power supply, monitor health of AC line, state of interlock inputs and internal 24V power supply load.
Fig 5-5 "Power Supply Controller" window
Behavior of “Turn power supply ON/OFF” button is equivalent to manual switching of power key on PHAROS power supply. If power supply was switched on from computer and key remains in position “Power OFF” to turn off laser move key to position “Power ON” and then back to “Power OFF”.
49
CAUTION: PHAROS
ELECTRONICS PREVENTS IMMEDIATE LASER SHUTDOWN IF
CURRENT ON
LD BARS IS NOT SWITCHED OFF. I N THIS CASE CURRENT ON
LD BARS IS DECREASED TO 0 AND ONLY THEN POWER SUPPLY AND LASER ARE SWITCHED OFF .
SHUTDOWN PROCEDURE CAN TAKE UP TO 1 MINUTE.
Button “Parameters” allows to access power supply parameters responsible for AC line health monitoring.
5.3.3 “Environment” window An “Environment” window is used to monitor PHAROS environmental parameters like temperature of LD bars, humidity inside Oscillator and RA and to control chiller parameters. (Only Termotek chiller is supported).
Fig 5-6 "Environment" window
To change chiller water temperature set point: enter a new temperature value and press “Set New Water Temp.” button.
50
5.3.4 “Osc./RA Bar Driver” window Two separate windows allow controlling LD bars current, monitoring actual current and voltage values.
Fig 5-7 "Osc Bar Driver" window
To turn LD bar on: Press button “On”. Status label will change color to orange while current is setting and then to green when current is set. To turn off LD bar off: Press button “Off”. Status label will change color to grey while current is decreasing. To set a new current value: Enter a new current value to edit box and press button “Set” or use scroll bar. (Arrow keys or mouse scroll button can be used to change current if scroll bar is selected).
5.3.5 “Oscillator” window “Oscillator” window displays actual oscillator output power, state of mode locking and Power-lock. If modes locking is active in oscillator label “Modes locked” is highlighted. Label “Setting power” indicates state of Power- Locking regime. To activate oscillator’s starter: press button “Run Starter”. “Starter runs” flag will be highlighted until starter stops. To set a new Power- Lock set point value: enter new value in milliwatts and press button “New Power Target”. Faster way to accept actual output power value as set point is to press button “Lock Actual Power”. To activate Power-Lock function: press button “Activate Power Setting”.
51
Fig 5-8 "Oscillator" window
5.3.6 “RA” window “RA” and “Sync Failures” windows are important while controlling RA. “Failures” window displays content of Timing Electronics Module failures register. Check boxes on the left side of window allow masking some failures. RA won’t stop on failure that is masked. Boxes on the right side displays accumulated failures. Accumulated values can be important while determining reason of RA malfunction or stop.
Fig 5-9 "RA" and "Sync. Failures" windows
To start RA: press button “Start”. To open Pulse Picker: press button “Open PP”.
52
To change cavity dumping time: press button “Cavity Dumping Time” and use scroll bar to change delay value. To set a new Power- Lock set point value: enter new value in milliwatts and press button “Set”. To activate Power-Lock function: press button “Lock”.
5.4 Protection of laser configuration parameters PHAROS system parameters are stored in internal flash memory of different controllers. All parameters can be scanned and saved to computer disk using menu command Service Save settings to file.
CAUTION! IT IS HIGHLY RECOMMENDED TO BACKUP LASER PARAMETERS TO FILE AND STORE IT IN SAFE PLACE.
Some laser parameters can be changed without disturbing laser functionality. Other parameters are defined by laser design and modification of these parameters can cause serious damage to PHAROS system. To prevent intentional or unintentional modification of critical system parameters, access levels are defined for every laser parameter. There are three different access levels used in PHAROS system:
“User Access Level”. This level is turned on by default when PHAROS system is powered on. It allows changing only basic set of parameters needed for day-to-day laser operation.
“Technician Access Level”. When enabled this level allows to modify all important laser parameters, that are not predefined by device design.
“Manufacturer Access Level”. When enabled, all PHAROS system parameters can be modified without restrictions.
Access level is set for all PHAROS controllers simultaneously by sending special code sequence on CAN bus. Access level remains unchanged until another correct sequences will be received or until power off operation. On power on laser always starts with “User Access Level”. All PHAROS internal controllers ignore parameter change commands if appropriate access level is not set. 53
User can change access level from remote control module or using PHAROS application on computer. To change laser access level from PHAROS application press toolbar button with key or select Service Access Level menu option. Choose radio button with access level, enter 4digit security code and press “Exit” button. If code is right- required access level will be set, else access level will be reset to “User Access Level”.
Fig 5-10 Setting access level with PHAROS application.
PHAROS application monitors system access level and disables modification of parameters if appropriate access level is not selected. Actual access level is displayed in main PHAROS application window caption.
Fig 5-11 PHAROS access level indication
Security code for “Technician Access Level” is 5172.
54
6 Remote Control Module Remote control module is small attachable unit with touch-sensitive LCD panel and knob. It provides fast and convenient access to major PHAROS control functions and can be used to perform all manual day-by-day operations. Module boots up in 10 seconds after laser is turned on and is capable to execute all main PHAROS control operations.
Fig. 6-1. Remote control module
6.1 Oscillator control Left side of LCD panel displays Oscillator tab after remote control module has started. This tab is main window for monitoring parameters and control of oscillator. It displays: -
Oscillator output power measured by internal oscillator power meter,
-
Target power value used as set –point for Power-Locking function,
-
Temperature of oscillator LD bar,
-
Amplitude of Narrow Bandwidth Detector in stretcher/compressor,
-
States of mode locking, Power-Lock and starter.
55
Fig. 6-2 Oscillator control window
Buttons and knob are used to access oscillator control functions: To set a new Power-Lock target value- Press button “Target power” and rotate knob keeping button pressed. Release button when “Target power” box will display required power value. To set actual power value as Power-Lock target value- Press and release “Target power” button without rotating knob. Actual Oscillator output power value will be set as target for Power-Lock. To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button. To activate oscillator starter- Press “Starter” button. “Starter is running” label will be displayed on the top- right corner of tab until starter will stop. To changed oscillator’s LD bar current- Press “LDD” button to access LDD control window. To changed oscillator’s parameters- Press “Parameters” button to access “Oscillator parameters” window.
56
6.2 RA control To access RA controls select tab “RA” on the main remote control module window.
Fig. 6-3 RA control window
Buttons and knob are used to access RA control functions: To start RA- Press button ‘Start RA”. To open Pulse Picker- Press button “PP Enable”. To set a new Power-Lock target value- Press button “Target power” and rotate knob keeping button pressed. Release button when “Target power” box will display required power value. To set actual power value as Power-Lock target value- Press and release “Target power” button without rotating knob. Actual RA output power value will be set as target for PowerLock. To start/stop Power-Lock function- Press “Enable/Disable PowerLock” button. To change RA LD bar current- Press “LDD” button to access LDD control window. To changed RA parameters- Press “Parameters” button to access “Oscillator parameters” window. To change cavity dumping time- Press “Sync params” button and select “Delay” button on menu window.
57
6.3 LDD control Control of Oscillator’s and RA LDD is performed from similar windows accessed by pressing “LDD” button on Osc and RA tabs.
Fig. 6-4 Oscillator and RA LDD control windows
To start/stop LDD bar current- Press button “LDD ON”/”LDD OFF”. To change LDD current: press button “Set I” and use knob to increase or decrease current. Push button “Fine” for fine current adjustments or “Coarse” for fast current changing,
58
7 Cables and connections
PHAROS is packed with all necessary and optional cables that can be used with the system. If user wants to use “Interlock” or “Emergency Stop” functions, plugs supplied on the rear panel of power supply can be used to produce customized cables. Check Fig 7-1 for connections between PHAROS sub units.
10
1
11
4
2
5 6
7
3 8
9
To laser
Remote panel can be connected to power supply or directly to laser. CAN bus terminator mus be plugged to power supply if remote panel is connected to laser.
Fig 7-1 Rear panel of PS01-3 power supply
59
All connections from power supply are made on the rear panel. Table 7-1 contains description of all sockets and used cables.
Table 7-1 Description of cables used with PS01-3
No.
Name
1
Control lines
2
Control lines
3
LDD outputs
4
COM port
5
Chiller
6
Interlocks
7
Safety Lock
8
9
AC input
10
AC output
11
AC output
Description
Cable code
Control cable from power C02.01 supply to laser Control cable for Remote C02.05 Control Module
Notes
Required only if Remote Control Module is used. Otherwise CAN bus terminator must be plugged in instead.
High current cable to LD C03.01 bars Serial data cable from PS01- C02.02 3 to computer
Required only if PHAROS is controlled using RS-232 interface Serial data cable from PS01- C02.02 Required only for 3 to Termotek chiller Termotek chiller control. Plug for level 1 and 2 INTERLOCK User must connect own interlocks inputs and laser cable to access interlocks status output. function. Plug for “Emergency User must connect own Shutdown” button cable to use “Emergency shutdown” function. USB cable from PS01-3 to Required only if computer PHAROS is control using computer. PS01-03 power supply AC C01.01 input (C20 socket) (European) C01.02 (USA, Japan) C01.03 (UK) AC output with C13 socket Common output from sockets 10 and 11 must not exceed 10A. AC output with C13 socket Common output from sockets 10 and 11 must not exceed 10A
60
7.1 Interlocks and “RA state” indication Interlocks can be connected to DB9 male socket located on rear panel of PHAROS power supply. Typical interlock application would be connection of breaker activated by opening doors in laboratory or any protective cover on laser mounting frame. Two levels of interlock function are implemented in PHAROS power supply.
Fig 7-2"Interlocks" connector Table 7-2 Description of "Interlocks" pins
Interlock level Level 1
Pins on DB9 connector 1,6
Level 2
3,7
Connection type Normally connected Normally connected
Reaction to disruption Stops RA
Procedure of deactivation Connect pins 1 and 6 back Stops RA and LD Connect pins 3 and drivers 7 back and switch power supply off – on.
Disrupting connection between two pins in interlock socket activates interlock function. Interlock action is fully controlled by mains controller and can be adapted according to user requirements. On standard model activated interlock Level 1 stops RA (if running) and Level 2 interlock stops RA and LD drivers. To deactivate Level 1 interlock it is enough to connect pins 1 and 6. To deactivate Level 2 interlock pins 3 and 7 must be connected and power supply must be switched off and on. CAUTION! INTERLOCK
PINS ARE GALVANICALY ISOLATED FROM OTHER
ELECTRICAL CIRCUITS .
CURRENT
PHAROS
IN INTERLOCK CIRCUIT NEVER EXCEEDS
1 MA.
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Fig 7-3 Interlock input circuit
Pins 4, 9, 5 on “Interlocks” socket are connected to the relay and can be used to get “RA state”.
Table 7-3 "RA state" pin out
State of RA
Pair of pins 4 and 9
Pair of pins 5 and 9
RA stopped
closed
opened
RA started
opened
closed
Fig 7-4 "RA state" output circuit
Note: Maximum relay settings are 0.5A/ 30V DC and 0.15A/ 125V AC.
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8 Timing Electronics Module (TEM) PHAROS RA operation is controlled by Timing Electronics Module. TEM is responsible for these functions:
Synchronizes RA operation to Oscillator optical pulses,
Controls RA and PP optical gates (Pockels cells),
Protects RA components from optical damaging.
TEM is designed as aluminum box fitted on oscillator side plate.
Fig. 8-1. External view of TEM
Table 8-1 contains description of all TEM inputs and outputs.
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Table 8-1. Description of TEM inputs and outputs Name
Direction
OUT PD
Input/ Output
RA LVL
Input/ Output
OSC SYNC
Input/ Output
NB
Input
OUT1
Output
IN1
Input
RA ON RA OFF PP ON PP OFF
Output Output Output Output
CAN
Outputs
CTRL
Description 50 Ohm coaxial input/output for PHAROS output photodiode. Signal from photodiode is retransmitted as output for user control. 50 Ohm coaxial input/output for RA level photodiode. This sensor is used to protect RA from too high energy pulses inside RA. Signal from photodiode is retransmitted as output for user control. 50 Ohm coaxial input for oscillator output photodiode. Signal from this photo diode is used to synchronize RA. 50 Ohm coaxial input for photodiode used as RA seed signal spectrum width monitor. Photodiode detects the power of the edge of seed pulse spectrum to prevent narrow spectrum (and as result short pulse) signal injection into the amplifier. Output to LED used for laser state indication. Input for cover switch (safety interlock) 50 Ohm 5V coaxial output to RA Pockels Cell driver. 50 Ohm 5V coaxial output to RA Pockels Cell driver 50 Ohm 5V coaxial output to PP Pockels Cell driver 50 Ohm 5V coaxial output to PP Pockels Cell driver Internal CAN bus connectors for communication with other PHAROS components. 24V power and CAN bus inputs from power supply
Input
SCOPE
Output
SYNC1
Output
SYNC2
Output
REMOTE
Outputs/Inputs
50 Ohm 2.4V coaxial user’s output. This output can be programmatically configured to monitor different signals. Output is source terminated and can be used on high resistance load as 5V output. 50 Ohm 2.4V coaxial user’s output. This output can be programmatically configured to monitor different signals. Output is source terminated and can be used on high resistance load as 5V output. 50 Ohm 2.4V coaxial user’s output. This output can be programmatically configured to monitor different signals. Output is source terminated and can be used on high resistance load as 5V output. PHAROS external control interface connector.
Onboard connector type MMCX socket
MMCX socket
MMCX socket
MMCX socket
Tyco MicroMatch socket Tyco MicroMatch socket MMCX socket MMCX socket MMCX socket MMCX socket IDC10 socket Tyco AMP TERMI-BLOCK header MMCX socket
MMCX socket
MMCX socket IDC14 socket
Outputs from TEM and some additional photodiodes are located on aluminum panel fitted on the rear side of PHAROS head (see Fig. 8-2 Error! Reference source not found.). 64
Fig. 8-2. PHAROS user outputs panels (standard and OEM versions) Table 8-2. Description of TEM inputs and outputs
Name
Direction
Description
Onboard connector type
PD OUT
Output
PD RA
Output
PD OSC
Output
50 Ohm coaxial output from PHAROS output photodiode. 50 Ohm coaxial output from RA photodiode. This sensor is used to monitor laser pulses inside RA cavity. 50 Ohm coaxial output from oscillator output photodiode.
BNC socket BNC socket BNC socket
50 Ohm 2.4V coaxial user’s output. This output can be SCOPE
Output
programmatically configured to monitor different signals. Output is source terminated and can be used on high
BNC socket
resistance load as 5V output. 50 Ohm 2.4V coaxial user’s output. This output can be SYNC1
Output
programmatically configured to monitor different signals. Output is source terminated and can be used on high
BNC socket
resistance load as 5V output. 50 Ohm 2.4V coaxial user’s output. This output can be SYNC2
Output
programmatically configured to monitor different signals. Output is source terminated and can be used on high
BNC socket
resistance load as 5V output. REMOTE
Outputs/Inputs
CTRL
Inputs
PHAROS external control interface connector.
DB15 socket
CAN bus and 24V supply inputs from power supply.
Tuchel 5 pins socket
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8.1 Principle of operation
Fig. 8-3. Structure of TEM
TEM can be controlled over CAN bus (using commands sent from computer or other device connected to the CAN bus) and from external laser control interface (using electrical signals). TEM enters “RA Stopped; PP Closed” state after power-up. If oscillator is operational and signal “OSC SYNC” meets amplitude, duration and period requirements, TEM can start laser. After receiving “RA Start” command TEM sends RA ON signal enabling amplification of oscillator’s pulse inside RA. After some period of time RA OFF signal is sent and light pulse leaves RA. Time between RA ON and RA OFF is increased with every laser shot from some initial value to the value defined by Cavity Dumping Time. This process is called “Soft start” and typically takes ~ 5 seconds. During this time laser output energy varies. After “Soft start” is finished, time interval between RA ON and RA OFF signals becomes equal to Cavity Dumping Time and laser output power stabilizes. If pulse picker is installed, “PP Open” commands changes TEM state to “RA Stopped; PP Opened” and two additional signals PP ON and PP OFF are generated to open and to close pulse picker. If “RA Stop” command is received, TEM finishes amplification cycle of last laser pulse and enters “RA Stopped; PP Closed” state. Next start command can be issued only after 3 seconds! “RA Stopped; PP Closed” state is also entered if TEM detects error or failure.
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RA Stopped PP Closed Error or failure
RA Start command
RA Started PP Closed
PP Close command
PP Open command
RA Started PP Opened
RA Stop command
Fig. 8-4. TEM state diagram (commands are sent by CAN)
8.2 Timing of laser control signals Fig. 8-5 shows the timing diagram of TEM generated control signals with reference to optical pulses of OSC and RA. Oscillator period OSC): time interval between two laser pulses at the oscillator’s output. Oscillator‘s train is monitored by OSC SYNC photodiode. This signal is also retransmitted for user control (see Fig. 8-5). Typical oscillator period is 13-14 ns. Laser Sync (SYNC): signal used to trigger amplification of oscillator’s pulse inside RA cavity and emitting it from laser. Sync signal source can be internal or external generator. It takes ~6 OSC periods after Sync is received to synchronize to oscillator. Laser Sync period can have values from 1000 s (corresponds to 1 kHz repetition rate) to ~1 s (1 MHz repetition rate). After receiving Laser Sync signal and completion of synchronization to oscillator’s pulses TEM generates 500 ns duration SCOPE pulse to user’s output. From this moment additional delay tON is generated before RA ON signal is send to RA Pockels cell driver (RA ON delay). RA ON delay can be adjusted between 0 and 45ns. RA OF delay (tOFF)- this parameter is used in “Soft Start” procedure. Difference tOFF- tON is used as intial Cavity dumping time (tCD) value. In ~5 seconds time Cavity dumping time is increased from (tOFF- tON ) to tCD. Cavity dumping time (tCD) is delay between RA ON and RA OFF signals. During this time laser pulse is amplified inside closed RA cavity. Cavity dumping time can be increased from 145 ns to 500 ns increasing laser pulse energy. This value is reached after “Soft Start” procedure. Pulse picker offset (tPP offset) is adjustable delay between RA OFF and PP ON pulses. tPP offset can be adjusted from -30 to 30 ns. PP OFF delay to PP ON (tPP OFF) is adjustable delay between PP ON and PP OFF pulses. HV driver delay (tDR)- is Pockels cell driver reaction delay to control pulses. Timing parameters of signals are presented in the Table 8-3.
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osc
Osc train Lase r Sync Default user’s outputs
tS1
SYNC
SCOPE SYNC1 (= RA ON) SYNC 2 (= RA OFF) Outputs can be reconfigured by user to another signals.
t ON RA ON
tOFF RA OFF RA Pockels Cell voltage
t DR
tDR
RA train
tPP offset PP ON
t PP OFF PP OFF
tDR
PP Pockels Cell voltage
tDR
t OUT PHAROS output
Fig. 8-5. Laser timing diagram
Table 8-3. TEM timing parameters min Oscillator period SYNC period SCOPE to Sync delay RA on delay RA off delay Cavity Dumping Time HV driver delay Pulse picker offset PP OFF delay to PP ON SCOPE, SYNC1 and SYNC2 delay to PHAROS output “Soft Start” time Time between RA Stop and Run commands
τOSC τSYNC tS1 tON tOFF tCD tDR tPP offset tPP OFF
typ
max
jitter
13-14 1-5*
1000 6 τOSC
0 145 145
45 500 500
1 τOSC 1 τOSC 0.5 (typical) 0.5 (typical)
60 -30
30 10 0.5 (peak to peak at 107 pulses)
tOUT 5 3
ns μs ns ns ns ns ns ns ns ns s s
* Depends from laser model Overall thermal peak to peak stability 500 ps in 5 -75 °C range.
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Fig. 8-6. OSC SYNC photodiode output
8.3 Pulse Picker operation modes Pulse Picker can operate in two modes: “closed window” and “shifted window”. When “closed window” mode is selected, PP Pockels cell is always closed in “PP Closed” state. This mode ensures maximal laser output contrast, but because of changing load on Pockels cell driver’s high voltage power supply there is some output pulse energy instability ~1 ms after PP is opened. If “shifted window” mode is selected, PP Pockels cell is opened and closed with every RA output pulse, but phase of PP operation is shifted to prevent RA pulses to be emitted in “PP Closed” state. This mode guaranties output pulse stability, but laser output contrast is lower.
Fig. 8-7. PP operation modes
There is one more PP mode called “OPEN mode”. In this mode PP is opened together with RA start signal. This regime is only used while adjusting RA timing parameters. See Chapter 8.5 for more details about PP mode selection.
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8.4 External laser control interface Three main PHAROS control operations: synchronization of laser pulses, starting/stopping of RA and opening/closing of Pulse Picker can be performed with electric signals using external laser control interface. External control interface must be enabled and configured using computer and PHAROS control application or other user written software. See Chapter 8.5 for more details about external interface configuration.
RA Disabled
RA Stop command
RA Start/Stop commands
PP Disabled
PP Close command
PP Open/Close commands
Error or failure
RA Enabled
PP Enabled
„RA on“ signal on DB15 connector
„PP on“ signal on DB15 connector
RA Running
RA Running PP Opened
Fig. 8-8. TEM states diagram with external RA and PP control enabled
If external RA and/or PP control sources are selected, “RA Start” and/or “PP Open” commands must be issued to allow laser control from external control interface. Fig. 8-8 presents diagram of TEM states when external RA and PP control sources are selected. “RA Start” and “PP Open” commands are transmitted over CAN bus from PHAROS control application or user’s software. PHAROS external control interface is realized as DB15 connector 1 9 SYNC IN 2 10 RA on/off 3 4
11 PP on/off
with three logical inputs and three outputs. Fig. 8-9 shows electrical circuit of external control interface inputs and outputs.
12 RA STATUS 5 13 SYNC OUT 6 14 FAIL 7 8
Fig. 8-9. Pin out of PHAROS external control interface DB15 connector
15
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Fig. 8-10. Electrical schematic of external laser control interface inputs and outputs.
Descriptions and requirements for control inputs and outputs are listed in Table 8-4. Table 8-4. Pin assignment of the REMOTE connector (DB15)
Pin No
In/ Out Signal
1,2,3,4,5 ,6,7 8 9
-
GND
IN
N.C. SYNC IN
10
IN
RA on/off
11
IN
PP on/off
12
OUT
RA STATUS
13
OUT
SYNC OUT
14
OUT
FAIL
15
-
N.C.
Description
Input of the external clock for the laser synchronization – initiates sync* of the laser. Input must be stable continuous frequency f=1200kHz (or 1 MHz depending on laser configuration). Duration of the high level must be between 100 ns and 500ns. Starts (low level) and stops (high level) RA operation. Stops RA operation starting from the first valid sync* of the laser. Start – initiates “Soft Start” of RA (RA STATUS output can be used to monitor when RA is leaving “Soft Start” and starts operating in a defined regime. The signal controls the pulse picker (low level – opened, high level closed). The status is loaded with valid laser sync* transition. High level indicates that RA is operating in a defined regime (soft start has finished and there are no fails in the system). Output of laser sync* signal triggered by the internal laser oscillator or SYNC IN. In a case of external clock the pulse duration is the same as input pulse duration. If SYNC IN is < 500ns then SYNC OUT is extended to ~500 ns. In case of internal clock SYNC OUT is ~500 ns. Indicates fail of the laser (OSC or RA). When Fail is high RA is stopped. When fail returns to low RA on/off rising transition will start RA operation.
*laser sync is internal synchronization signal in the laser. It can be produced by internal clock of the laser or external SYNC IN signal.
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The diagram of remote laser control signals and laser output pulse timing is presented in Fig. 8-11. Fig. 8-12 presents the waveforms for laser remote control signals. The table below contains the required signals parameters.
Fig. 8-11. Timing of remote control signals and laser output
72
Fig. 8-12. Waveforms for laser remote control
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Table 8-5. Parameters of signals for laser synchronization from external device min
typ
max
Internal synchronization SYNC OUT high
tp
500
ns
PP on/off signal delay
tpr1
0
130
ns
PP on/off signal hold
tPP
50
70
ns
External synchronization SYNC IN high SYNC IN period
tih
100
500
ns
til+ tih
1-5*
1000
s
SYNC IN to SYNC OUT delay
tio
100
SYNC OUT high
toh
PP on/off signal delay in level control mode
tPD1
PP on/off signal hold starting from SYNC IN in level control mode
tPP1
560
PP on/off signal delay in edge control mode
tPD2
50
100
ns
PP on/off signal hold in edge control mode
tPP2
50
70
ns
500
ns tih if>500
ns
150
ns ns
*Depends from laser model Note: Exact timing parameters can vary depending from TEM firmware version.
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8.5 Controlling TEM parameters Control of laser parameters can be performed by mean of PHAROS application started on computer connected to PHAROS laser. TEM is controlled from RA window. This window is used to start/ stop RA, open/ close PP, change cavity dumping time and access other TEM parameters.
Fig. 8-13. Main RA and TEM control window
Pressing “TEM Parameters” button opens “TEM v.2 Parameters” window (see Fig. 8-14).
Fig. 8-14. TEM parameters window
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“Configuration” frame is used to control PHAROS external control interface modes. These parameters can be accessed in Technician and Manufacturer access levels.
“Enable external RA start source”- if checked, DB15 input “RA on/off” is used to start/ stop RA. Additionally button “Enable” in RA window is used to allow DB15 operation. “Enable external Pulse Picker control source”- if checked, DB15 input “PP on/off” is used to open/ close PP. Additionally button “Enable PP” in RA window is used to allow DB15 operation. “Enable external sync source”- if checked, DB15 input “SYNC IN” is used to trigger RA shots. “Invert RA and PP control levels”- if checked, DB15 inputs “RA on/off” and “PP on/off” are inverted: low level starts/enables RA/PP and high level stops/disables RA/PP. “Synchronous RA mode”- if checked and external RA sync source is not selected, oscillator’s output pulses are used as RA sync source. Changing of RA frequency means changing of oscillator’s output pulses divisor factor in this regime. RA frequency control Enable external sync source flag Synchronous RA mode flag
Internal TEM generator Laser sync in Pulses from oscillator output
Divider
Pulses from DB15 SYNC IN
Fig. 8-15. Configuring laser sync sources
“PP mode” frame allows selecting between two PP regimes: “closed window” and “shifted” window. Check chapter “Pulse Picker operation modes” for more details. “RA frequency control” frame is used to control TEM internal frequency generator/ oscillator’s pulse divider. “External RA frequency source control” displays actual “SYNC IN” input frequency and value of “Locked external frequency”. If “SYNC IN” frequency differs from “Locked external frequency” more than 10% RA is stopped and failure “Frequency out of locked range” is activated. “SCOPE SYNC source”, “SYNC1 source”, “SYNC2 source” frames control multiplexer of user’s outputs (TTL levels).
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Table 8-6. Signal sources for “SCOPE SYNC”, “SYNC1” and “SYNC2” outputs
Signal name
Description
Int_Gen
Signal from internal RA frequency generator.
OSC_SYNC
TTL version of OSC_SYNC input of TEM.
RA_ON
Copy of “RA ON” signal used to trigger RA Pockels cell.
RA_OFF
Copy of “RA OFF” signal used to trigger RA Pockels cell.
PP_ON
Copy of “PP ON” signal used to trigger PP Pockels cell.
PP_OFF
Copy of “PP OFF” signal used to trigger PP Pockels cell.
SYNC2
Signal with user controllable delay locked to “RA OFF” signal.
RA_rdy
Internal TEM signal.
RA_delay_rdy
Internal TEM signal.
SYNC_OUT
Copy of “SYNC OUT” output on DB15 connector.
RUNNING
“RA STATUS” output on DB15 connector.
RA_Overrun
“RA frequency overrun” failure output.
Power_OK
“5V supply failure” output.
RA_Fail
“RA common failure” output.
OUTPUT_PD_CMP0
Internal TEM signal.
OUTPUT_PD_CMP1
Internal TEM signal.
RA_LEVEL_CMP0
Internal TEM signal.
RA_LEVEL_CMP1
Internal TEM signal.
Narrow_Spectrum_Level_OK
“Narrow bandwidth” failure output.
oclk
Internal TEM signal.
osclk_b
Internal TEM signal.
oclk_c
Internal TEM signal.
prd_invalid
Internal TEM signal.
prd_valid_gate
Internal TEM signal.
Osc_period_short
“Osc sync period too short” failure active signal.
Osc_period_long
“Osc sync period too long” failure active signal.
oclk_bad
Internal TEM signal.
oclk_active
Internal TEM signal.
oclk_rdy
Internal TEM signal.
DB15_SYNC_IN
Copy of “SYNC IN” input on DB15 connector.
DB15_PP_IN
Copy of “PP on/off” input on DB15 connector.
DB15_RA_IN
Copy of “RA on/off” input on DB15 connector.
RA_OPEN
Output active from “RA ON” until “RA OFF” signals.
PP_OPEN
Output active from “PP ON” until “PP OFF” signals.
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“RA adjustments and timing” frame contains one check box and three sliders. These parameters can be accessed in Technician and Manufacturer access levels. “Pulse Picker OPEN mode” check box allows enabling additional PP mode. If checked, PP is opened before RA Pockels cell. This regime is used while adjusting TEM timing parameters. Sliders ”RA On delay”, “RA Off start” and “PP Offset” change corresponding timing parameters t ON, tOFF, tPP OFF.
Check Chapter 8.2 for more details.
“Oscillator Sync adjustments” frame contains two controls to adjust “Osc Sync Level” parameter and “Osc too short/ too long” failure value. Button “Tune to Osc” locks TEM to oscillator repetition rate (this operation must be performed if oscillator was readjusted or changed). “Narrow bandwidth failure” frame allows to adjust NB photodiode level when “Narrow bandwidth failure” is activated. “RA level too high” is used to adjust “RA level too high” failure and warning levels. Modification of other TEM parameters can be achieved by accessing “TEM v.2 Advanced Properties” window by mean of pressing button “Advanced”. This button is accessible only in Manufacturer access level.
Fig. 8-16. “TEM v.2 Advanced Properties”
8.6 TEM failures/ warnings flags TEM state is displayed as set of 12 different failure/ warnings flags.
RA common failure General failure indicates that RA was stopped because of some failing behavior. The reason of failure can be detected by the state of other failure flags.
RA level too high-warning Warning indicates that radiation level inside RA cavity reached defined warning level. Active warning doesn’t stop laser.
RA level too high-failure Failure indicates that radiation level inside RA cavity reached failure level. If enabled, this failure stops RA. 78
RA frequency overrun Failure indicates that RA cavity dumping time is too long for actual frequency. If enabled, this failure stops RA. If disabled- some laser pulses are missed.
Frequency out of locked range Failure indicates that RA Sync signal is routed from external interface (DB15 connector) and its frequency differs from previously locked value more than 10%. If enabled, this failure stops RA.
Osc sync failure General failure indicates that Osc. Sync signal from oscillator is missing, has too low/ too high amplitude, irregular period or oscillator is in double pulse mode. If enabled, this failure stops RA.
Narrow bandwidth failure Failure indicates that narrow spectrum detector inside stretcher/compressor reached critical value. If enabled, this failure stops RA.
Osc sync period too short This warning indicates additional information about Osc. Sync signal amplitude and frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too short” parameters must be adjusted to clear this warning.
Osc sync period too long This warning indicates additional information about Osc. Sync signal amplitude and frequency. It doesn’t stop laser. “Osc. Sync level” and “Osc. Sync Period too long/ too short” parameters must be adjusted to clear this warning.
5V supply failure Failure indicates that there is problem with TEM electronics power supply circuits. This failure always stops RA
RA LDD stopped Failure indicates that RA laser diodes driver was stopped before stopping RA. If enabled, this failure stops RA.
Osc LDD stopped Failure indicates that Oscillator laser diodes driver was stopped before stopping RA. If enabled, this failure stops RA.
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